The disclosures of Japanese Patent Application Nos. Hei 9-176594 filed on Jun. 18, 1997, Hei 9-176590 filed on Jun. 18, 1997, and Hei 9-177775 filed on Jun. 19, 1997, each including the specification, drawings and abstract, are incorporated herein by reference in their entirety.
1. Field of Invention
The present invention relates to an automotive impact energy absorbing structure and, more particularly, to an impact energy absorbing structure for absorbing impact energy applied to an upper portion of a body of a motor vehicle from inside a compartment, using an energy absorbing member that deforms to absorb the impact energy applied thereto.

2. Description of Related Art
Japanese patent application laid-open Nos. Hei 8-119047 and Hei 8-127298 propose automotive energy absorbing structures for absorbing impact energy using a resin-made energy absorbing body (for example, a grating-like rib) that is disposed in a space between a pillar having an inner panel and a pillar garnish disposed at a passenger compartment interior side and separated from the inner panel by the space.
If the energy absorbing body is formed as a resin-made grating-like rib member, the amount of energy absorbed by the member during an initial period of application of impact energy is relatively small since plastic deformation of the resin-made grating-like rib member starts late relative to the amount of deformation. Furthermore, the resin-made grating-like rib member is subject to changes in load bearing strength due to temperature or humidity changes and, in some environments, tends to deteriorate over time, thus resulting in a decreased capacity for energy absorption. Therefore, in designing energy absorbing resin-made grating-like rib members, the dimensions thereof are determined so that the members remain able to absorb desired amounts of energy even when they deteriorate. Thus, the energy-absorbing members inevitably become large in size.
Accordingly, it is an object of the present invention to provide an automotive impact energy absorbing structure in which the time until the start of plastic deformation relative to the amount of deformation during an initial period of application of impact energy is shortened while retaining an intended energy absorption capacity, and which allows a size reduction of an energy absorbing member.
It is another object of the invention to provide an automotive impact energy absorbing structure that allows adjustment of an energy absorbing characteristic.
It is still another object of the invention to provide an automotive impact energy absorbing structure that allows the deforming direction of the energy absorbing structure to be forcibly determined by an interior member disposed at a compartment interior side of the energy absorbing member.
According to a first aspect of the invention, there is provided an automotive impact energy absorbing structure including a structural member provided in an upper part of a vehicular body. The structure member has an inner panel. An interior member is spaced from the inner panel by an interval extending therefrom toward the inside of a compartment. A hollow body made from metal is disposed in the interval.
According to a second aspect of the invention, there is provided an automotive impact energy absorbing structure including a structural member extending in an upper portion of a vehicle body, in a lengthwise direction, and an interior member spaced from the structure member by an interval extending therefrom toward an inside of a compartment. A hollow body made from metal is disposed in the interval. The hollow body is adhered to the interior member so that an axis of the hollow body extends in a lengthwise direction relative to the structural member.
According to a third aspect of the invention, there is provided an automotive impact energy absorbing structure including a structural member extending in an upper portion of a vehicle body in a front-and-rear direction relative to the vehicle body. The structural member includes a panel. An interior member is spaced from the panel by an interval extending therefrom toward an inside of a compartment. The interior member is formed so that the thickness of the interior member in a section taken on a plane perpendicular to an axis extending in a lengthwise direction relative to the structural member varies locally. A hollow body made from metal is disposed in the interval and fixed to the interior member.
According to the first aspect of the invention, if a load equal to or greater than a predetermined value is applied to the hollow body, the hollow body deforms, thereby absorbing impact energy.
According to the first aspect of the invention, the hollow body has a greater ductility than a grating rib, and starts to plastically deform at an earlier timing relative to an amount of displacement. Therefore, the hollow body can sufficiently absorb impact energy during an initial period of load application. Furthermore, the hollow body may have a closed configuration in a section taken on a plane perpendicular to the axis of the hollow body. Then, it becomes easier to adjust the size of the area that receives load or the size of the area that transmits load imposed on the hollow body to the inner panel.
The hollow body may also be formed by extrusion forming, and can easily be formed into a desired configuration or desired dimensions. Therefore, it becomes possible to reduce changes in the energy absorbing characteristics depending on the direction of load application by forming an entire configuration of the hollow body that is optimal in accordance with the interval between the structure member and the inner panel, by locally changing the thickness of the hollow body, or by forming a rib standing in the hollow of the hollow body.
Since the hollow body is not substantially affected by atmosphere temperature or humidity, there is only a small change in load bearing strength due to temperature or humidity and substantially no deterioration over time due to the environment. If the hollow body is formed from aluminum by extrusion forming, it is possible to re-process or reshape a hollow body deformed for absorption of impact energy, for reuse, since aluminum is suitable for recycling or reuse.
According to the second aspect of the invention, the interior member and the hollow body have different ductilities. Therefore, if a load equal to or greater than a predetermined value is transmitted to the hollow body by the interior member, a relative displacement occurs at adhering portions between the two members so that the sheering force based on the relative displacement acts on the adhesive. The reaction force to the sheering force at the adhering portions between the interior member and the hollow body also absorbs impact energy, thereby achieving energy absorbing characteristics different from the original energy absorbing characteristics of the hollow body. Furthermore, a change in the adhering manner can also change the energy absorbing characteristics.
Since the hollow body can be formed into any desired sectional shape, the hollow body can easily be adapted to the interval between the structure member and the interior member. Furthermore, because it is possible to select a location of adhesion to the interior member and an adhesion area from a wide range of choices, and because it is possible to achieve various characteristics by selecting a wall thickness or a sectional shape of the hollow body, the degree of freedom in selecting energy absorbing characteristics is high.
The interior member may be attached to the structural member as follows. First, an adhesive is applied to required portions of the interior member, and then the hollow body is adhered to the interior member by the adhesive. Alternatively, after the hollow body is placed on a required location on the interior member, an adhesive is applied to adhere the hollow body to the interior member. After that, the interior member, together with the hollow body, can easily be attached to the structural member.
According to the third aspect of the invention, if a load equal to or greater than a predetermined value is applied so that the interior member deforms, the hollow body fixed to the interior member is displaced together with the interior member in the direction of the load. When the hollow body contacts the panel of the structure member, the hollow body starts to plastically deform, absorbing impact energy.
According to the third aspect of the invention, the thickness of the interior member locally varies. If a load is applied to a portion of the interior member that is remote from the thinnest portion of the interior member, the interior member deforms with the thinnest portion acting like a fulcrum. As the interior member thus deforms, the hollow body is displaced toward the panel of the structure member. Therefore, it is possible to forcibly restrict a portion of the hollow body that deforms, by using the interior member. If a load is applied to the thinnest portion of the interior member, the entire interior member is displaced in the direction of the load, thereby deforming the hollow body. Therefore, it is easy to provide an energy absorbing body with an amount of displacement, a shape and the like which are required for energy absorption. Thereby, a sufficient amount of energy absorption can be secured. Furthermore, since there is no need to provide a hollow body with deforming characteristics in accordance with various load directions in order to secure a required amount of energy absorption, the configuration and structure of the energy absorbing body can be simplified.